The invention relates to a digitally controlled analog switch and more particularly relates to an analog switch system for digitally controlling the transmission of one of a plurality of analog signals along a single output conductor.
Heretofore, one technique for controlling the transmission of analog signals between two points has utilized electromechanical switches. However, the reliability of electromechanical switches leaves something to be desired. Such switches may not always switch properly and the mechanical components of such switches may stick in one position causing the switch to remain in an ON or OFF state. For example, the mechanical reeds in a micro-reed relay sometimes become welded together sticking the switch in an ON position.
Further, contact noise is developed from contact closure in mechanical switches which gives rise to error voltages introduced into the analog signal whose transmission is being controlled. Also, external temperature may affect the mechanical operation and noise generation of some mechanical switches.
In an effort to overcome the disadvantages of mechanical switches, electrical switches are sometimes used. Electrical switches may be described as switches with no mechanically moving parts. However, due to the electrical nature of such switches, offset voltage errors and other types of signal noise from the electrical switch are imparted into the analog signal whose transmission is being controlled. Thus, it is highly desireable to have a switch which is capable of passing an analog signal free of noise signal errors.